WASHINGTON - An American college student imprisoned by North Korea and in a coma for more than a year was freed Tuesday and arrived last night in his home state of Ohio.

Secretary of State Rex Tillerson announced that North Korea released Otto Warmbier, 22, a University of Virginia student, who was serving a 15-year sentence for alleged anti-state acts. His parents, Fred and Cindy Warmbier, said their son has been in a coma since March 2016. "We learned of this only one week ago,” they said in a statement.

A plane carrying Warmbier arrived around 10:20 p.m. CT Tuesday at Cincinnati's Lunken Airport. Two ambulances met the plane on the runway to transfer Otto to the hospital.

Officials worked quietly as reporters and photographers watched from behind a fence. At 10:42 p.m., the ambulances drove away.

During his 18-month incarceration, the Warmbiers heard from Otto only once, through a letter on March 2, 2016.

It was apparently shortly after that date that Otto fell ill. Some media reports said the North Koreans suggested Otto had come down with a case of botulism and fell into a coma after being given a sleeping pill. Former United Nations Ambassador Bill Richardson and others have questioned that account.

Charlotte Simons said she was just leaving a Pilates class in Hyde Park Tuesday morning when her phone lit up with the news Otto was coming home.

It was 10:10 a.m., Simons said.

She pulled off to the side of the road to read the reports.

Simons is close friends with Otto’s aunt, she said, and she also worked with Otto’s mother. She was elated.

Quickly, that elation turned to dread as details emerged and Simons learned of the coma. She was sick all day, she said. She struggled Tuesday night to find the words.

“I can’t even imagine,” she said. “... I just want to take their pain.”

Hours before Otto was scheduled to land, there was a row of reporters standing outside the airport, lined up facing the runway.

A police officer stood guard nearby.

The ambulances waited quietly, lights and engines off.

Farther back, standing just outside the “Welcome to Cincinnati” sign on the airport terminal, Simons and other well-wishers gathered.

They let out a small cheer as the plane taxied up the runway.

Tillerson said the State Department secured Warmbier's release at the direction of President Trump. The announcement came shortly after former NBA player Dennis Rodman arrived in Pyongyang for a return visit to North Korea. But Rodman, who has visited with North Korean leader Kim Jong Un, said the issue of four Americans detained by the North is "not my purpose right now."

State Department spokeswoman Heather Nauert later said Rodman "had nothing to do with" Warmbier's release.

Earlier Tuesday, Fred Warmbier told The Cincinnati Enquirer that the family will hold a news conference later this week in Cincinnati.

Nauert would not say anything about Warmbier's health because of privacy concerns.

"What an incredible day for one of our citizens who was held in North Korea for more than a year," Nauert said. "I’m not going to characterize what their son has been through."

She said U.S. officials had a difficult time getting information about Warmbier from North Korea. The U.S. does not have diplomatic relations with the reclusive country and works through Sweden to deal with North Korean officials. U.S. officials last had consular access to Warmbier on March 2, 2016, through the Swedish Embassy in Pyongyang, Nauert said.

Former United Nations ambassador Bill Richardson, who has been trying to help secure Warmbier’s release, said North Korea's health system is “very primitive,” and the circumstances surrounding the student's condition are murky.

“This is a matter of grave concern,” Richardson said. “How did he fall into a coma? And why was this not disclosed?”

Sen. Rob Portman, R-Ohio, confirmed the release but did not comment on Warmbier's health.

“Fred, Cindy, and the Warmbier family have been remarkably strong throughout this ordeal. Over the last 18 months, they have had to endure more than any family should have to bear,” Portman said in a statement.

The Warmbiers have been pressing — first behind the scenes and then more publicly — for their son’s release.

Phil Robertson, deputy Asia director at Human Rights Watch, said, "It's clear that Pyongyang has committed a grave injustice against Otto and his family, and the news that he may be returning with a serious medical problem raises concerns about what happened to him in North Korean custody."

Tillerson said the State Department is still working on the release of the three other U.S. citizens detained in North Korea.

"We strongly suggest that Americans do not go to North Korea," Nauert said.

Warmbier was a University of Virginia undergraduate when he decided to go to North Korea with a tour group. He was detained as the tour group prepared to leave the country. In a televised trial, he was sentenced in March 2016 to 15 years in prison with hard labor as he publicly confessed to trying to steal a propaganda banner.

"The UVA family will continue to keep the Warmbiers in our thoughts and prayers as Otto returns to the United States and his home where he will receive the care and support of those who love him," university President Teresa Sullivan said in a statement Tuesday.